1. Field of the Invention
The invention relates to a device for forming metals, in particular forming of parts, such as the forming of a collar.
2. Description of the Related Art
The forming of a collar on a workpiece made of steel, for example a steel sheet plate made of the material of the plate, is an important topic. See DE 10 2006 029 124 B4 as well as DE 1 916 826, for example. The workpiece is placed on a die. The die includes a bore, which is adjacent to the workpiece. A hole is then pressed into the workpiece by means of a tipped punch while material is drawn into the die bore out of the sheet metal plane. As a result, a collar is formed which remains part of the workpiece. The above principle is particularly used in the automobile industry.
The described forming process involves stress to the workpiece within the forming zone. As such, mainly tensile stress take effect when raising the collar in the sheet metal edge. The reachable collar height is limited. The smaller the ratio between collar diameter to collar height, the higher is the risk of a breaking of the material in the collar region.
Forming failures are a big problem. Occasionally, this is not recognized before using the workpiece. Disassembly of defective parts and replacement with flawless parts is particularly complex in such a case.
It has already been attempted to optimize the drawing process by application of heat. For example, the punch can be heated in order to apply heat to the forming zone of the workpiece, e.g. the sheet metal plate. However, this provides the disadvantage that the punch loses its strength because it is heated and thus only has a short service life.
JP-A-2009262184 discloses a device which uses heat. By way of said device, a pot-type object is heated prior to a forming process. To that end, electrodes need to be advanced to the workpiece and then removed again in order to make room for advancing a tappet together with a punch. Processing is thus divided into two stages, which implies time effort.
JP-A-2007260761 describes a device which includes two electrodes for heating a steel sheet. When heating said sheet, first a tappet needs to be lifted and then lowered again after heating. This also requires time.